// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_SYNCHRONIZATION_LOCK_IMPL_H_
#define BASE_SYNCHRONIZATION_LOCK_IMPL_H_

#include "base/base_export.h"
#include "base/macros.h"
#include "build/build_config.h"

#if defined(OS_WIN)
#include <windows.h>
#elif defined(OS_POSIX)
#include <pthread.h>
#endif

namespace base {
namespace internal {

    // This class implements the underlying platform-specific spin-lock mechanism
    // used for the Lock class.  Most users should not use LockImpl directly, but
    // should instead use Lock.
    class BASE_EXPORT LockImpl {
    public:
#if defined(OS_WIN)
        using NativeHandle = SRWLOCK;
#elif defined(OS_POSIX)
        using NativeHandle = pthread_mutex_t;
#endif

        LockImpl();
        ~LockImpl();

        // If the lock is not held, take it and return true.  If the lock is already
        // held by something else, immediately return false.
        bool Try();

        // Take the lock, blocking until it is available if necessary.
        void Lock();

        // Release the lock.  This must only be called by the lock's holder: after
        // a successful call to Try, or a call to Lock.
        void Unlock();

        // Return the native underlying lock.
        // TODO(awalker): refactor lock and condition variables so that this is
        // unnecessary.
        NativeHandle* native_handle() { return &native_handle_; }

    private:
        NativeHandle native_handle_;

        DISALLOW_COPY_AND_ASSIGN(LockImpl);
    };

} // namespace internal
} // namespace base

#endif // BASE_SYNCHRONIZATION_LOCK_IMPL_H_
